While fatty acid soap is known to be an efficient, inexpensive cleansing product, it can also be harsh (e.g., non-mild) to the skin. The short chain (e.g., C14 and below, primarily C12 and below) and unsaturated long chain (e.g., sodium oleate) soaps, for example, provide good lather and detergency, but can also be harsh and drying.
Applicants have noted that removal of the generally more soluble, harsher components noted above from a soap chain distribution do not generally affect the structuring and the processing properties of a bar (which properties are more dependent on the less harsh, insoluble, longer chain soaps), but could affect, for example, lather properties.
One major challenge, therefore, is to find a bar which is made from fatty acid soap stock (it should be noted that unsaturated, more soluble soaps such as, for example, oleate, generally are derived from the same source as longer chain, insoluble soaps, i.e., from non-nut oils such as tallow or palm) which stock can be used to make bars which process well, retain good foam properties and which have desirable mildness properties.
Applicants have now found it is possible to create a precursor bar formulation from fatty acids and/or fatty acid soaps having no more than a certain mol % unsaturated chain length components and, of the remaining mol % saturated components, substantially no component of chain length C14 or below (except for residual or artifact components which are extremely difficult to eliminate from the added synthetic surfactant altogether; these may comprise less than about 1% preferably less than 0.5% of the stock and are preferably absent and, in any event, would result in more than 1% of any C14 or below fatty acid or soap components in the final bar).
The precursor bar, which acts as a kind of matrix for additional components to be blended or mixed into the final bar, can be formed in one of two ways. First, it can be formed by mixing/blending the unsaturated fatty acid (0 to 12.5 mol %), saturated fatty acid of chain length C16 and up (50 to 87.5 mol %) and caustic (12.5 to 50 mol % of, for example NaOH or KOH) depending on extent of desired neutralization in the precursor matrix. In a second embodiment, it can be formed by mixing pre-formed soap with fatty acid so that no neutralization with caustic is required.
When a final bar comprising 40 to 88% by wt. fatty acid soap and/or fatty acid (at 50 mol % caustic, assuming made by neutralization method, there is 100% neutralization and bar is 100% soap; at less caustic, there is mixture of soap and fatty acid) of this precursor is blended/mixed with synthetic, water and filler, unexpectedly it has been found that the bar processes well (firmness of at least 100 kPa using cheese wire measurements) and has exceptionally good lather (bar lather assessment greater than 50 ml by prescribed methodology) as well as desirable potential mildness.
Thus, in one embodiment of the invention, a precursor bar/matrix formulation is made by formulating 0 to 12.5 mol % unsaturated fatty acid (e.g., oleic acid); 50 to 87.5 mol % saturated fatty acid of chain length C15 to C24, preferably C16 to C20; and 12.5 to 50 mol % caustic (depending on level of desired neutralization). The key is to form a precursor as “clean” as possible to the extent is has substantially no soaps or fatty acids (if undemeutralized) with chain length C14 or below. When such precursor/matrix is later blended with other bar components, it will process well and, even in substantial absence of soluble fatty acid acid/soap (except for what may be brought in by other bar components other than those firming the precursor) unexpectedly provide excellent foaming.
In a second embodiment, the same “clean” precursor is formed but it is formed by blending pre-formed soap and free fatty acid (again with 0-12.5 mol % unsaturates and substantially no chain length components C14 and below) without caustic to neutralize.
In effect, applicants have found a bar which can be made from non-nut oils (usually defining a mix of soluble, unsaturated; and insoluble longer chain saturated fatty acid) rather than mix of tallow and nut oils (where shorter chain saturates are normally found).
When short chain length soaps (which provide good user properties) are minimized, use of synthetic (e.g., anionic) is one way to make up for the loss in the bar user properties. According to the subject invention, however, there is minimized both the use of short chain soap/fatty acids and of synthetic surfactants (which may enhance other properties such as foam, but may also be harsh), while maintaining good user properties.
U.S. Pat. No. 5,387,362 to Tollens et. al discloses bars containing tailored mixtures of Mg++, Na+ and K+ ions to react with lauric acid, select C14-C18 fatty acid and oleic acid. In the subject invention, lower chain length fatty acid (e.g. lauric) are minimized or substantially absent. Also, Tollens appears to be a pure soap bar composition while the bars of the subject invention require at least above 7% by wt. synthetic.
U.S. Pat. No. 5,262,079 to Kacher et al. discloses partially neutralizing mono carboxylic acids to form framed bars with high levels of anionic and nonionic firmness aids. The subject invention minimizes levels of synthetic (less than 25%, preferably less than 22%, more preferably 20% or less) and does not require firmness aids. It is also an extruded bar. The Kacher bars also must use above 15% water.
U.S. Pat. No. 6,121,216 to Narath et al. describes enhanced processing by minimizing soap level. The subject invention does not seek to minimize soap, but to offer beneficial soap blends.